Hi Krzysztof, > So, with one transaction, can I write an arbitrary number of bytes to > the device, and then, in the same transaction, can I read one (or no, > or with some controllers, more than one) byte(s) back? In I2C mode, you can even alternate as many read and write sequences you want in a single transaction. The target chip would of course need to know how to interpret such a transaction though. I've never seen this possibility used so far. In SMBus mode, you are limited by the transaction types that have been defined, but a number of them are composed of a write transaction and a read transaction (separated by what is known as a "repeated start"). Read Byte, Read Word, Read Block and Read I2C Block are such transactions. See the SMBus specification for the details. > Interesting. Still, that limits it to 8-bit-addressable EEPROMs. Depends on the SMBus. A SMBus controller could implement 16-bit address I2C block transfers. I don't think I saw one do so far, but it's still possible in theory. Also note that this can easily be emulated using a Write Byte command (which writes 2 bytes on the bus) to set the 16-bit addressed EEPROM offset, then using continuous Receive Byte commands to get the data. This is of course slower than a block read though. > Are such things documented somewhere on the net (some datasheet > maybe)? The I2C specifications are available from Philips. The SMBus specifications are available from smbus.org. Intel also has good datasheets for all ICH chips. http://www.semiconductors.philips.com/markets/mms/protocols/i2c/ http://www.smbus.org/specs/ More generally, see the lm_sensors project's links page: http://www2.lm-sensors.nu/~lm78/cvs/lm_sensors2/doc/useful_addresses.html and also: http://secure.netroedge.com/~lm78/docs.html Hope that helps, -- Jean Delvare
